It is common to need to deliver a fluid product to a destination through the use of a pump. Of course, many varieties of hydraulic pumps exist for this purpose. Many of these hydraulic pumps are driven by electricity or another external power source.
In certain circumstances, it is necessary to be able to deliver a precise amount of fluid product to a fluid supply line without a power source other than the fluid supply line itself. This is possible in the situation where the fluid supply line, or fluid line, has a variation in pressure and the fluid product to be delivered can be injected in concert with such variations in fluid line pressure.
This may be necessary, for example, for a washing machine, such as a commercial dishwashing machine, which undergoes repeated fill and drain cycles over time. First, such washing machine may fill with water from a supply line under pressure for a wash cycle. Typically, detergent of some type is added to the water during this cycle. Once full, pressure in the water supply line is reduced, or eliminated, due to the shut-off of a water fill valve, which isolates the water supply line to the dishwasher from the external water supply system. After the wash cycle is complete and the machine has been allowed to drain, or has been pumped out, the machine may again fill with water from water from a, typically the same, supply line by increasing the pressure in the line. This is typically done with a fill valve that regulates pressure in the water supply line. The water used in this cycle could be for a rinse. Typically, it is desirable to add a rinse aid agent to the water in the machine during the rinse cycle. These cycles could be repeated as repeated loads of dishes are processed through the machine. Of course, the two cycles, one wash and one rinse, is merely exemplary. More than one wash cycle could be used. More than one rinse cycle could be used. And additional cycles or different cycles could be used. The constant important item is the need to add some product, e.g., detergent or rinse aid agent, to the water during a given cycle and the water used in the machine came from supply line with cyclic pressure (due to the need to repeatedly fill and drain the machine).
At the same time, such washing machines may not come equipped with equipment to automatically add a precise amount of such products appropriately for each cycle. Adding such automatic equipment to existing machines is difficult, in part because of the difficulty of obtaining an electrical power source and, even if available, an electrical hydraulic pump adds to the complexity, cost and detracts from the reliability of such machine. Even if such washing machines were initially equipped with such automatic equipment, again it would add to the complexity and cost and detract from the reliability of the machine to use an electrically powered hydraulic pump.
Unfortunately, there have not been too many options available.
One type of self-powered, i.e., powered from cyclic pressure of the supply line itself, hydraulic pump makes use of a Bellofram™ diaphragm and an internal spring in a mechanically complicated mechanical hydraulic pump. Such a pump has been used by Ecolab, Inc., St. Paul, Minn., in a pump system known as an Eco-Vac™ pump. While this hydraulic pump system works well, it is significantly complicated and significantly expensive.